Interlocking IM nails with threaded guidewire

ABSTRACT

This invention provides for a new method for locking Intramedullary Nails (IM Nails) with Threaded Guidewire which may be accompanied by specially designed tapered screws with segmented threads. This new design uses the screws to begin locking the IM Nail, followed by threaded guidewire that is placed in between screws of the IM Nail. Whenever a more proximal screw is placed with the threaded guidewire, it causes the guidewire to push/lock onto or around the distal screw eliminating the play and causing a more stable form of fixation. The screws may be tapered and have partial, segmented or full threads. The tapered end would pass through the guidewire eliminated early locking. The middle threads would engage the guidewire and IM Nail. The tapering and threading would allow for maximum screw strength, a lag effect, centering of the IN Nail and fixation to the nail. The wider end of the screw would eliminate movement of one end of the screw, while the other end will rely on the guidewire to eliminate play.

APPLICATION DATA SHEET

Not Applicable

SPECIFICATION

An Intramedullary Nail (IM Nail) is inserted into the cortical bone. TheIM Nail is secured by screws and threaded guidewire; this will secureand eliminate movement of the screws to the IM Nail. The IM Nail willhave a guidewire track through the inside that connects each of thescrew openings. Upon insertion of the first most distal screw that willbe locked to the nail is placed, a threaded guidewire is insertedthrough the slot of the Intramedullary Nail. The more proximal screwwill exert a force that pushes the threaded guidewire into the moredistal screw and cause the guidewire and distal screw threads tointerlock. The exerted force of the more proximal screw is caused by thelength of the threaded guidewire. When the proximal screw is tightened,it pushes the guidewire down further to the distal screw causing asecure or interlocking connection. The distal screw may or may not befurther secured by tightening/turning of the proximal screw such that itfurther pulls the guidewire around the distal screw aiding in locking.

The interlocking may occur due to the pressure of the guidewire,wrapping of the guidewire around one or both of the screws, throughperforations within the screw, or other means that results ininterlocking. There may be alternative means of pushing the threadedguidewire into or around the more distal screw and causing interlocking.Direct manual pressure applied on the guidewire may cause the guidewireto break as the proximal screw is inserted, or an alternative mechanismmay push the threaded guidewire into the more distal screw and causethem to interlock. Additionally, the guidewire may be curved on thebottom or have a y shape in order to aid locking around the most distalscrew.

The screw may also be designed such that it is tapered and hassegmented, partial or full threading. The tapering would ensure theinitial threads on the tip pass through the guidewire without earlygripping. The middle threads would engage the guidewire and the IM Nail.The wider end of the screw would eliminate movement of one end of thescrew, while the other end will rely on the guidewire to eliminate play.

This process is repeated for additional screw sets so that the mostproximal screw will always lock in the previous screw placed in. Thefinal screw can be locked with an end cap that has a threaded tip thatcan exert more pressure on the most proximal screw. This method can beused in conjunction with other locking mechanisms.

TITLE OF INVENTION

A new method of locking Intramedullary Nails is to use threadedguidewire. The threaded guidewire is placed in between screws of anintramedullary nail. Whenever a more proximal screw is placed with theguidewire, the more distal screw is locked to the nail. In addition,movement or play of the more proximal screw is minimized. This newdesign including both the guidewire and screw locks the screw in placeto eliminate this play and result in a more stable form of fixation.

CROSS REFERENCE TO RELATED APPLICATIONS

Provisional Patent Application No.: 60/459,953 with a filing date ofApr. 4, 2003 (submitted by inventor of this application).

U.S. Pat. No. 6,019,761, dated Feb. 1, 2000 suggests interlocking byusing guidewire that goes in through the IM Nail holes, up or down theIM Nail and out the next hole.

U.S. Pat. No. 6,524,314, dated Feb. 25, 2003 suggests interlocking byusing 2 lag screws and a locking screw through the IM Nail.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

The current methods of fracture reduction are:

-   -   Casts/braces    -   Plates:        -   Conventional        -   Locking    -   External fixation    -   Intramedullary Nails        Intramedullary Nails have several advantages over other forms of        fixation:    -   they are less invasive than plates;    -   they have a lower infection rate;    -   nails are stronger than the plates;    -   nails have a mechanical advantage compared to plates;    -   the screws used with nails are more resistant to breakage due to        the decreased moment arm;    -   screws may be placed in different planes;    -   nails have a high rate of union;    -   nails allow for anatomic reduction;    -   cast/braces immobilize the limb and do not allow early motion;    -   external fixators have a risk of pin tract infections.

One of the current method of interlocking IM Nails is to solely usescrews, which can result in loss of reduction because of the inherentplay in screw-nail interface. A second way of interlocking IM Nails isto cap the screw at the contra lateral cortex, which increases fixationin the cortical bone; however, does not help the screw-nail interface;additionally, pressure applied by the capping on one end may cause thedistal end to move out of position. A third available way ofinterlocking IM Nails is to have the hole of the IM Nail lined withrubber to provide a more grippable material for the screws; however, theinherent play in rubber does not provide sufficient locking. The rubberline IM Nails also have the possible for foreign body reactions withflaking of the rubber.

This new mechanism, with threaded guidewire in between the screws, locksthe screw in place to eliminate this play and result in a more stableform of fixation.

Two other patented ways of interlocking IM Nails were found, however,neither are currently marketed:

-   -   An interlocking Intramedullary Nail (U.S. Pat. No. 6,524,314,        granted Feb. 25, 2003) provides for a different mechanism, using        2 lag screws and a locking screw. This product is currently not        marketed; however, this would be a difficult mechanism because        there are only a couple of safe zones where screws can be        placed. With the addition of 2 screws placed for fixation, it        may be difficult to find safe zones. Additionally, the may cross        thread early prohibiting further insertion.

An interlocking Intramedullary Nail (U.S. Pat. No. 6,019,761, grantedFeb. 1, 2000) provides for interlocking by placing a guidewire throughone screw hole up to and out of the next. This patent also relies ondrilling holes versus already manufactured holes and dropping wiresthrough the holes and using the screws to cause the wires to interlockto the screws. This patent has a complete different means by which theinterlocking would occur and be enhanced.

BRIEF SUMMARY OF THE INVENTION

This invention provides for a new method for locking IntramedullaryNails (IM Nails) with Threaded Guidewire. The current methods ofinterlocking screws has inherent play in the screw-nail interface andtherefore can result in loss of reduction. This new design uses screwsto begin locking the IM Nail, followed by using threaded guidewire thatis placed in between screws of the IM Nail. Whenever a more proximalscrew is placed with the threaded guidewire, it causes the guidewire topush/lock onto or around the distal screw eliminating the play andcausing a more stable form of fixation.

The screws may be tapered and may be partially, segmented or fullythreaded. The tapering and threading would allow for maximum screwstrength, a lag effect, centering of the IM Nail and fixation to thenail.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1. Page 1: Diagram of showing the first, distal screw placement andguidewire track

-   -   1.Cortical Bone    -   2.Guidewire Track    -   3.First locking screw inserted    -   4.Intramedullary Nail

FIG. 2. Page 2: Diagram of placement of threaded guidewire throughguidewire track to first distal screw.

-   -   1.Threaded guidewire    -   2.Guidewire track opening for placement of guidewire    -   3.Threaded guidewire against first distal screw    -   4.First distal screw

FIG. 3. Page 3: Diagram of all screws and guidewire placed between eachscrew; each screw is secured by the guidewire force onto the screw orwrapping around the screw

-   -   1.First distal screw    -   2. Second screw (proximal to first distal, distal to third        screw)    -   3.Third screw    -   4.Fourth screw    -   5.Cortical bone    -   6.Intramedullary Nail    -   7.Threaded guidewire placed between all screws

FIG. 4. Page 4: Diagram of side view of how the guidewire wraps orpushes against the threads of the placed screws.

-   -   1.Joint of guidewire and screw    -   2.Design of an alternative tapered screw that has segmented        threads for maximum interlocking.    -   3.The widest end of screw has large threads to grip to the bone    -   4.The middle threads are finer to engage the guidewire    -   5.The tapered end threads are larger to grip bone; however, the        tapered end allows guidewire to pass by the guidewire to        eliminate early locking/gripping.

DETAILED DESCRIPTION OF THE INVENTION

The IM Nails and screws are manufactured with cobalt-chrome, titanium,stainless steel or other materials for strength and durability and bodycompatibility. The threaded guidewire is manufactured from the samematerials.

The combination of the screws and threaded guidewire eliminates play inthe fixation to maintain reduction. The current methods do not addressscrew-nail interface locking. and can cause loss in reduction.

After insertion of the Intramedullary Nail (IM Nail) into the corticalbone, the first, most distal screw is placed. A threaded guidewire isplace down the inside of the IM Nail through a guidewire track. Theplacement of the next, proximal screw pushes the guidewire into, onto oraround the first distal screw causes a stable interlock. The distalscrew may or may not be further secured by tightening/turning of theproximal screw such that it further pulls the guidewire around thedistal screw aiding in locking.

The interlocking may occur due to the pressure of the guidewire,wrapping of the guidewire around one or both of the screws, or othermeans that results in interlocking. There may be alternative means ofpushing the threaded guidewire into or around the more distal screw andcausing interlocking. Direct manual pressure applied on the guidewiremay cause the guidewire to break as the proximal screw is inserted; oralternative mechanism that will push the threaded guidewire into themore distal screw and cause them to interlock. Additionally, theguidewire may be curved on the bottom or have a y shape in order to aidlocking around the most distal screw.

The screw may also be designed such that it is tapered and hassegmented, partial or full threading. The tapering would ensure theinitial threads on the tip pass through the guidewire without earlygripping. The middle threads would engage the guidewire and the IM Nail.The wider end of the screw would eliminate movement of one end of thescrew, while the other end will rely on the guidewire to eliminate play.

This process is repeated for additional screw sets so that the mostproximal screw will always lock in the previous screw placed in. Thefinal screw can be locked with an end cap that has a threaded tip thatcan exert more pressure on the most proximal screw. This method can beused in conjunction with other locking mechanisms.

This invention will provide for the most stable reduction that maintainsthe advantages over the current and alternative means of reducingfractures

1. A mechanism to secure Intramedullary Nails by using threadedguidewire between screws that secure and interlock the screws when asecond proximal screw is placed as it will cause the guidewire topush/lock onto, around or through the distal screw. The mechanismimmobilizes the Intramedullary Nail by eliminating screw-nail play tomaintain fracture reduction.
 2. A mechanism of using a tapered screwwith segmented threads and a guidewire between screws to lockIntramedullary Nails. The guidewire is placed after the distal screwplacement and is locked onto, around or through both the distal andproximal screw upon placement of the proximal screw. The tapered screwswith segmented threads allow for maximum screw strength, a lag effect,centering of IM Nail and engagement of both the IN Nail and threadedguidewire, thus immobilizing the IM Nail by eliminating screw-nail play.3. Use of using a tapered screw with segmented threads to interlock IMNails using any other or no other alternative mechanism. The taperedscrews with segmented threads allow for maximum screw strength, a lageffect, centering of IM Nail and engagement of the IN Nail.